Blower structure and method of fabrication



Oct. 27, 1959 s. CAMPBELL ,9 0,224

BLOWER STRUCTURE AND METHOD OF FABRICATION Filed Nov. 17, 1953 3 Sheets-Sheet 1 IN VEN TOR.

qzyffimpez ATTORNEYS.

Oct. 27, 1959 s. P. CAMPBELL ,2

BLOWER STRUCTURE AND METHOD OF FABRICATION Filed Nov. 17, 1955 s Sheets-SheetZ IN V EN TOR.

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ATTORNEYS.

Oct. 27, 1959 s. P. CAMPBELL 2,910,224

BLOWER STRUCTURE AND METHOD OF FABRICATION Filed Nov. 17, 1953 I 3 Sheets-Sheet 5 ,f'gjfi ,fgze TYP/CAL BLOWERS CAMPBELL DES/5N I E E I 3f I I I PRESSURE PRESSUREl I BASH/NE i DISTANCE I I 5455 g i i D/S7I4NCE I 4 7 5/4 514 .54- -r1 4- I i i I l 1 (em/47E OF CHANGE BETWEEN vecrons INVENTOR.

ATTORNEYS.

Unite 1 BLOWER STRUCTURE AND METHOD OF FABRICATION Application November 17, 1953, Serial No. 392,601

4 Claims. or. 230-134 The invention relates to a blower structure and method of fabricating the same and, more particularly, to a centrifugal blower structure and method for securing the blower blades or vanes to the end pieces.

An object of this invention is to provide a novel blower structure and novel method of assembling the same. Another object of the invention is to provide a centrifugal blower that operates with a minimum of noise. Still another object is in the provision of a centrifugal blower wherein the blades are turned forwardly along the lateral outer edge portions thereof while the center portion of the blade has the customary curvature in a rearward direction with the result that the peak of the air distribution pattenn at the outlet is considerably reduced and made more uniform over the entire outlet area and noise substantially eliminated. Yet another object is in providing a blower blade with a compound curvature at the edge thereof whereby the blade is appreciably stiifened and a lighter gage metal may be used in forming the blade without increasing edge vibration thereof which causes noise. A further object of the invention is to provide a-method for quickly and easily and for positively securing the blower blades to the end pieces. Yet'a further object is to provide end pieces with depressed and slotted portions and the blower blades with laterally-turned tabs whereby the end pieces maybe secured to the blower blades in an easy assembly method. .Still a further object is in providing a method ofassembling a blower structure wherein the parts are all mechanically united, whereby heat applicationssuch as *welding, which causes warpage and distortion, etc.-are avoided. Additional objects and advantages will appear as the specification proceeds.

Embodiments of the invention are illustrated in the accompanying drawings, in which v Figure 1 is a longitudinal sectional view taken on the line 11 of Fig. 2; Fig. 2 is a side view in elevation with portions broken away to show the blower blade curvature; Fig. 3 is a perspective view of a blower blade; Fig. 4 is a broken sectional view showing ablower blade secured to an end piece; Fig. 5 is a perspective view of a blower embodying the invention and formed in accordance therewith; Fig. 6 is an exploded view showing the parts thereof in perspective; Fig. 7 is a perspective view showing the' step of securing a blower blade to the hubassembly; Fig. 8 is a broken perspective view showing a portion of an end piece in enlargement to illustrate clearly the depression and slot therein for receiving the tabs of the blower blades; Fig. 9 is a broken side view showing the step of bringing the end pieces into engagement with the blower blades; .Fig. 10 is a view similar to that of Fig. 9 and shows the tabs of the blower blades inserted through the slots in the end pieces; Fig. 11 is another view similar to the views of Figs. 9 and 10, and which shows the blower blades and the tabs thereof locked securely to the end pieces; Fig. 12 is a broken perspective view showing'a modified form of blower blade; Fig. 13 is a perspective viewshowing a modified type of spacer member; Fig. 14"

States Pate 0 is a broken transverse sectional view showing the blade at the outlet of my blower; and Fig. 17 is a vector diagram of the air distribution of my invention.

Referring first in particular to Fig. 6, which shows the parts of the blower in spaced-apart relation, it is seen that a pair of generally cup-shaped caps 10 are provided,

7 each of which has a central opening 11 therethrough. At

their inner ends, the caps 10 are provided with an annular flange 12 adapted to freely receive therein the ends of a tubular spacer member 13. A shaft 14 is adapted to be received within the openings 11 and to project therethrough. At one end, as can be seen best in Fig. 1, the shaft 14 is flared outwardy at 15 and abuts the wall of the cap 10 about the opening 11 therethrough. At its opposite end, the shaft is enlarged at 16 and a shoulder is thereby provided at the enlarged portion and against which the wall of the other cap member 10 abuts. The caps 10 with the spacer 13 therebetween are thereby locked upon the shaft. Preferably, the enlarged end portion of the shaft 14 slidably receives therein a splined bushing 17 that is adapted to receive the end of a motor 4, shaft or other power source that will drive the blower in a rotary movement. The bushing 17 may be located relative to the shaft 14 and secured thereto by means of a set screw 18.

A plurality of'spaced-apart vanes or blower blades 19 are adapted to be secured to the tubular spacer member 13 and caps 10. Preferably the blades are equally spaced and this is accomplished by equippingthe spacer member with a plurality of equally spaced ap art longitudinallyextending slots 20 therein that each receive a laterallyturned tongue 21 provided by the end portion 22 of each blade 19. By referring to Fig. 7 and also to Fig. 2, it will be seen that the tongue 21 projects into the interior of the tubularspacer 13 through the slots 20, while the tab or end portion 22 is adapted to lie against the peripheral surface of the spacer 13: The edges of the end portion 22 are received within the flanges 12 of the caps 10 and the blades are thereby locked in'position about the spacer 13, the edges being rigidly held between the spacer 13 and the flanges 12. It will be noted that the cut-outs 22a in the blades adjacent the end portion 22 permit this Each of the blades 19 flares outwardly from the narrow tab portion 22 or widens along eachlateral edge thereof. At the wide outer end of the blades and on each side thereof a tab or ear 23 is provided. The ears 23 are adapted to extend through slots provided by the end pieces 24 and to be rigidly secured thereto in a pressing operation. It isbelieved that reference to Fig. 4; will show the specific arrangement employedto secure the vanes or blades to the end pieces. It will. be seen'that.

each of the end pieces has a plurality of circumferentially spaced recesses 25 therein provided by striking outwardly the portions 26. During thestri-king operation wherein the bumps 26 are formed, a slot or slit 27 is provided through which the tab 23 of a vane may project. The

vanes are then rigidly secured to the end pieces 24 by pressing the portions 26 inwardly so that they abut the tabs 23, as is seen in Fig. 4, and by also pressing the tabs tightly against the central wall of the end pieces. Preferably a slot 27 is formed at each end of the bumpedout portions 26 and although the second slot is not used in the assembly operation, this construction permits the use of a single die to stamp the end pieces 24 which are, it will be apparent, in oppositely-facing relation in the structure.

' As will beseer'i best iifFi'gZ, the vanes 19 are aruate Patented Oct. 27, 1959.-

wardly-curved blower blades to discharge air outwardly as the blower rotates, with a relatively low velocity and relatively high static head. The direction of blower rotation is indicated by the arrow in Fig. 2. The vanes 19 curve rearwardly through the central portion 29, then, but it will be noted that along the lateral edge portions the vanes are curved forwardly at 30 to provide concave portions 31. In other words, then, the .vanes have a compound curvature and are arcuate and curve rearwardly throughout the center portion thereof and throughout substantially the entire vane area, but along the side edges thereof and adjacent the outer edge of the vane, the vanes are turned forwardly and discharge the air outwardly with a relatively high velocity but relatively low static head, Thus each vane provides both a convex portion throughout the center thereof and a concave portion along the lateral or side edge portions adjacent the outer end thereof. Fig. l is also believed to show this clearly and it is seen in this illustration that the blade 19 is quite wide along the outer edge thereof and then tapers inwardly along the curved edges 32 to provide the reduced end portion or tab 22. Centrally throughout the entire inner to outer length of the blade, the blade has a rearward curvature while adjacent the outer end and side edges the blades turn forwardly, as is indicated at 30.

In operation of the structure the blower is secured to a shaft that may be driven by a motor or engine or other power source. The blower will be suitably encased in a casing member provided with both inlets and outlets. As the blower rotates the blades 19 are operative to force air through the casing and outwardly through the discharge port or outlet thereof. This type of operation of the blower structure is conventional and therefore will not be further described.

Generally, blower blades are arcuate throughout their entire width and curve rearwardly so that a convex surface is provided over which the air flows with a minimum of frictional resistance. Thedifiiculty that has been encountered in such structures is that a greater mass or volume of air is discharged at the center portion of the blade than is discharged along the edges thereof. This uneven air distribution pattern results in the creation of noise that is objectionable since the decibel level is relatively high, particularly when the blower is used in an air heating or conditioning system wherein the noises developed are amplified and telegraphed through sheet metal conduits, etc. In my invention the blades 19 are each curved forwardly or in an opposite direction along the outer edges thereof so that a composite blade structure is formed having a compound curvature; one in which the central portion curves rearwardly while the edge portions thereof are turned forwardly. The blades are still operative to discharge a large volume of air but the discharge pattern is evened so that the peak near the center portion of the blade is not so pronounced and the operation of theblower, it has been found, is exceptionally quiet. The blower operates in a conventional manner, however, to draw in air'through an inlet, and to force it through an outlet and into a distribution system, etc. The leveling ofi of the peak of the outlet distribution pattern at the center portion of the blades and the increase of the low points of the distribution pattern has been found to lessen substantially the noise developed; yet the volume or mass of air discharged by the blower is not seriously affected.

A vector diagram showing the air flow from a blower blade incorporating my invention is illustrated inFig. 17. The blower blade shown in this figure is given the numeral 49. The blade 40 has a rearward curvature through the central portion thereof as indicated by the numeral 41 and has also a forward curvature along the edge portions thereof as indicated by the numeral 42.

4 The blower blade will rotate in a clockwise direction in the view of Fig. 17. The generally horizontal vector which is designated as tangent velocity represents the peripheral velocity of the blade 40. This vector is designated with the numeral 43. Vector 44 is representative of the velocity of the air flowing over or being discharged by the forwardly-turned edge portions 42 of the blower blade relative'to the tangential velocity of the blower blade. The absolute velocity of the air discharged by the forwardly-curved blade portions 42 is indicated by the vector 45 which is further designated in the figure as forward curve resultant. It is seen that the absolute velocity of the air is relatively large.

Vector 46 represents the velocity of the air being discharged over the rearwardly-turned portion 41 of the blower blade 40 relative to the tangential velocity of the blower blade represented by the vector 43. The absolute velocity of the air discharged over the rearwardly-curved blade portion 41 is the resultant vector 47 which is designated in Fig. 17 as backward curve; resultant. The angle 6 between the forward curve resultant vector 45 and the backward curve resultant vector 47 represents the rate of change between the vectors 45 and 47. It will be appreciated that the over-all air distribution and the velocity thereof of the blower blade;

40 can be controlled and changed by varying the point.

at which the blower blade changesfrom a rearward to, a forward curvature. That is to say, the velocity of the; air flow from the blade 40 will vary if the forward curvature commences closer to the center of the blade that is indicated in the drawings and, similarly, it will also be.

changed if the forward curvature begins closer to theside edges of the blade that is indicated in the drawings.

Such a change will of course alter the position of the; resultant vectors 45 and '47 and they can be brought.

closer together so that the angle 6 will be smaller, or canbe moved farther apart with the result that the angle 0.

The angle 0, then, represents the rate of change of the blower blade from a rearward to awill be larger.

forward curvature.

In Figs. 15 and 16 a pressure distribution curve atv the outlet of a conventional rearwardly-curved blower blade and a compound blower blade incorporating my invention are shown. In Fig. 15, for example, a blower is illustrated and is designated generally with the nu-- meral 50. The blower 50 has a plurality of blower blades or vanes 51. Each of the blades 51 has an overall width that is indicated by the dotted lines 51a extending from the upper blade to the pressure base line of the graph. The outer dotted lines represent extensions of the blower scroll outlet 51b, and air expands from the blower blades 51 into this space between the inner and outer dotted lines to fill the scroll. The blades 51 have a forward curvature. It will be clear from Fig .15

and from the curve 52 drawn on the graph that the greatest air pressure at theoutlet is at the center portion of the blade 51 and that the pressure drops off sharply and is approximately zero at the side edges of the blade. I have found that a pressure pattern or air distribution pattern of this character is undesirable, for it results in the creation of objectionable noise.

I have also discovered that blower noise can be lessened substantially if the air distribution pattern is leveled so these blades is indicated by the curve 55 on the, gra h The widthof the blades is shown by dottedlinesjkt:

extending from the upper blade to the pressure base line while the outer dotted lines represent extensions of the blower scroll outlet 54b. It can be seen that the pressure of the air discharge is fairly even and a considerable pressure exists at the side edges of the blade as well as at the center portion thereof. r h

A specific example of the results achieved from a blower incorporating my invention maybe helpful and will be set out as follows. A conventional blower having blades with a forward curvature and with a peripheral length of 2% feet maybe rotated to have a peripheral velocity of 2565 feet per minute. vThis-blower when rotatingat the indicatedvelocity was found to have a particular decibel rating. Thesefigures are set out to provide a standard or reference against which a blower incorporating my" invention. may be compared.

A centrifugal blower having a peripheral length of 2% feet and blades with a compound curvature that are turned rearwardly through the central portion thereof and forwardly at the side edges was rotated so as to have a peripheral velocity of 4312 feet per minute. The noise level produced by the centrifugal blower incorporating my invention was found to be slightly less than that of the smaller blower operating at a much smaller peripheral velocity and in fact was about. 180%. of the decibel rating of the standard smaller blower. Since the pressure is a function of the peripheral velocity of a centrifugal blower, it will be appreciated that the-pressure developed by the blower incorporating my invention is considerably higher than the pressure developed bythe conventional blower which must rotate at a slower rate of speed, for'if the peripheral velocity of theconventional blower becomes much in excess of 2565 feet per minute the noise level is objectionable. Therefore a blower having a-larger diameter can be rotated at a much greater speed with the result that the outlet pressure is substantially higher when such blower incorporates my invention. I 1

At the same time, the blower bla'des'of my invention may be made from metal-having aj much lighter gage than the gage necessitated in conventional blowers, because the compound curvature stiffens the blade at the outer edge thereof where the tendency to vibrate and thereby create noise is the greatest. The backward and forward curvature of the blade substantially stiifens the same and, then, as the result of the lighter gage metal that may be used, the cost of the blowers is decreased appreciably.

It has been found that the blower structure may be assembled quickly and easily if the steps set out in Figs. 5 to 11 are carried out. In the assembly operation, vanes 19 are provided equipped with the central tongue 21 and the tongue of each blade is inserted into a slot 20 provided by the spacer 13 to equally space the blades about the spacer. The blades 19 may be stamped and the tongue 21 formed as part of the stamping operation. Similarly, the ears or tabs 23 may also be formed in the single stamping operation. moved into position and the flanges 12 thereof receive and clamp the blades in position upon the spacer. The shaft 14 may then be inserted and the end thereof flared outwardly, as shown in Fig. l, to lock the caps in position.

The end pieces 24 are provided and these are stamped 'so that the portions 26 are struck outwardly therefrom.

As part of the stamping operation, the slots 27 may be formed adjacent the outwardly-struck portions 26. The tabs 23 of the vanes 19 are then turned laterally, as is indicated in the drawings, and the end pieces 24 brought into engagement with the blades 19, as is indicated in Fig. 9. It is noted in Fig. 9 that the tabs 23 fit nicely into the pockets or recesses 25 provided by the outwardlystruck portions 26 and that upon then turning the end pieces 24 relative to the blades, the tabs 23 move through the slots 27 and into the position illustrated in Fig 6 Next the caps are Thus there is no problem in accurately aligning the tabs 23 with the slots 27 provided in the end pieces, but a simple rotary movement of each of the end pieces relative to the vanes is effective to center and align the tabs with the slots and to insert the tabs therethrough. When this has been done the end pieces arerigidly secured to the vanes in a single pressing operation which is illustrated in Fig. 11,,and in which the tabs 23 are forced into tight engagement with the annular wall of the end pieces 24, and at the same time the outwardly-struck portions 26 are pressed inwardly so that they tightly abut the tab23 and vane juncture, and thereby prevent relative-move ment between the vanes and end pieces.

A modified form of blower structure is illustrated in Figs. 12 through 14. The modification includes a spacer member 13a that is cylindrical and is devoid of the slots 20 withwhich the spacer 13 was provided as has been hereinbeforeset out. The slots may be eliminated in the spacer 13a for they served only the function of orienting the blower blades inequally spaced relation about the spacer and in this modification I provide another means for'spacing the blower blades at proper intervals.v

As shown in Fig. 12, the blower blades 19a are equipped with; a tab 60 at the inner reduced end thereof thatiis turned laterally and is preferably provided with a' slightcurvature so that it will liefirmly uponthe peripheral'surfa'ce of the spacer 13a The tab 6 0:is provided with edge portions 61 that extend outwardly and are adapted to 'be received underv the flanges 12 of the end cap 10 in the same manner as has been before described. Each of the, end members 61 has a forwardlyextending edge 62 that is adapted to abut the upwardly-turned section 63 of the blower blade 19a positioned in front of it, as isindicated in Fig. 14. Thus itis seen that in Fig. 14 the tongue'or tab 60 of each of the blades 19a is received upon the peripheral surface of the, spacer 13a and/the dimensions of the e d ge po'rtion61 and edgeGZ thereof are selected so that the blower blades abut each other tightly about the spacer and are therefore equally spaced aboutthismember.

Thus I have provided a blower structure in which each of the blower blades has a compound curvature and is curved rearwardly through the central portion thereof and forwardly along the side edges thereof. The result is that a substantially even air distribution pattern at the blower outlet from edge to edge of each blower blade is achieved and this even air distribution pattern provides a blower structure that may operate with peripheral velocities far in excess of those reasonably attainable with conventional blowers and therefore the air pressure at the outlet, which is a function of the peripheral velocity, is much larger than that usually attained. At the same time, the noise level of the blower is less than the decibel rating of conventional blower designs and the problems of amplifying and telegraphing the noise through the distribution conduits of air heating and cooling systems is lessened appreciably. Further, the compound blade curvature stilfens or reinforces the blade at the outer end thereof where the tendency to vibrate is greater and thinner metal may be used in the blade construction without increasing the noise level of the blower. Further, a simple and easy method of assembling the blower is provided and one in which the use of heat such as for welding in the uniting of the various parts is eliminated so that warpage and distortion, etc., caused by the application of heat to the sheet metal parts is avoided and the blower may be both statically and dynamically balanced with ease, which further eliminates vibration and noise.

While in the foregoing specification a method of forming a blower structure, and the blower apparatus, have both been set out in detail for purposes of adequately describing my invention, it will be apparent to those skilled in the art that considerable deviation from these details may be made without departing from the spirit and principles of the invention.

, 7 I claim: H

1. A centrifugalblower, comprising a shaft adapted to be rotatably driven, a pair-of caps carried upon said shaft in spaced-apartrelation and each being equipped with an inwardly-turned flange, a spacer member interposed betweensaid caps and having end portions received within said flanges; a plurality of blower blades each equipped with a tab lying on the surface of said spacer having edge portions snugly received within said flanges, said blades having an ear along each side edge thereof, and a pair of end pieces provided with slots receiving said ears, each'of said blades curving rear wardly from the inner edge thereof adjacent said spacer meinber toward the outer edge thereof, the outer edge portion of eachblade being curved in a reverse direction to face forwardly whereby each of said blades is provided with a compound curvature operative to provide a relatively uniform air flow over the outer edge of the blade. 2. Ina centrifugal blower, a plurality of vanes each outwardly extending from the central hub, a pair of side rings joining the outer corresponding side portions of each vane, each of said vanes being curved rearwardly from the inner to the outer ends thereof in the portion intermediate the said side rings and being curved forwardly in two generally triangular portions thereof in the outer corners thereof, the outer endof each vane being substantially straight. v I r i '3. In a blower structure, a hub adapted to be rotatably driven, a plurality of blower vanescarried" by said" hub in substantially equally spaced relation about the circumvferential surface thereof, each of said vanes having an inner edge adjacent said hub and an outer edge spaced. from said hub with side edges extending between said inner and outer edges, each of said vanes having a rear-, ward curvature to provide throughout. the central portion thereofa generally convex configuration extending from jacent said outer edge portion to provide a generally concave configuration at the said side edges, and, a pair of side rings secured to said side edges of the vanes,

said hub including a spacer member equipped with end caps overlying annular portions of said spacer member, and said vanes beingequipped with tab portions adapted to lie upon said spacer and under said end caps and having a forward edge adapted to abut thevane just forwardly thereof, whereby the abutment of the tabs and vanes "about the spacer member establishes the spacing of the vanes thereabout'.

4. In a centrifugal blower, a central hub, a plurality of vanes extending outwardlyfrom said central hub, the portion of each vane secured to said hub being of reduced width compared with the outer edge portion thereof, a pair of side rings adjoining the sides of the wider outer corresponding edge portions of each vane, each of said vanes being curved rearwardly from' the inner to the outer ends thereof in the portion intermediate the said side rings and being curved forwardly in the portions thereof adjacent said side rings,'therearward curvature being most pronounced midway between the side rings and the forward curvature being most pronounced at the sides of the vanes, the outer'edge of each vanebeing substantially straight.

References Cited in the file of this patent UNITED STATES PATENTS 31,844 Y Willsont; Mar. 26, 1861 223,300 Smethells Jan. 6, 1880 918,559 Landis- Apr. 20, 1909- l,03'1,l80 Hancock July 2, 1912 1,445,176 Schmelzer Feb. 13,. 1923 1,462,557 Kuezel July 28, 1923 2,071,296- Connor-et a1. Feb. 16, 1937 2,115,367 Levy et al Apr. 26,- 1938 2,242,586v Marbach May 20, 1941 2,336,231 Dodge- Dec..7-,, 1943 2,457,265 Nygren Dec. 28,, 1948 2,745,171 King et al May 15', 1956 FOREIGN PATENTS 16,592 Great Britain, of 1908 

